docs: def register_epsf(self, epsf):
          """
          Register and scale (in flux) the input ``epsf`` to the star.
  
          Parameters
          ----------
          epsf : `EPSFModel`
              The ePSF to register.
  
          Returns
          -------
          data : `~numpy.ndarray`
              A 2D array of the registered/scaled ePSF.
          """
  
          yy, xx = np.indices(self.shape, dtype=np.float)
          xx = epsf._oversampling[0] * (xx - self.cutout_center[0])
          yy = epsf._oversampling[1] * (yy - self.cutout_center[1])
  
          return (self.flux * np.prod(epsf._oversampling) *
                  epsf.evaluate(xx, yy, flux=1.0, x_0=0.0, y_0=0.0))